This invention relates to an alignment-based rigid-body manufacturing plant, system and method.
Manufacturing systems and methods have heretofore been utilized in manufacturing plants. In an output-based organizing system manufacturing operations are categorized in terms of the types of outputs generated and the tools used in production. For example, the category xe2x80x9cmechanical joiningxe2x80x9d has the following sub-categories: pressure/cold welding, friction welding, ultrasonic welding, explosive welding, etc. Therefore, the number of distinct competencies is arbitrarily large, since outputs and tools continue to evolve (e.g., due to changes in technology). Such manufacturing line operations are often specific to the type of product or component being produced. Each line produces one type of product (where that product may be a finished good, a subassembly, or a component). Both xe2x80x9clinexe2x80x9d manufacturing and xe2x80x9cmodularxe2x80x9d manufacturing are fixed from this point of view, since in both cases, a line or cell is dedicated to a particular type of product, and therefore require re-configuration in order to produce a new product. Producing new products (or new models of the same product) requires different operations. Conventional manufacturing systems have low adaptability, since whenever a product or component is modified or added, a work center must be added or modified. This discourages plants or factories from producing multiple product lines, which restricts the capability of the manufacturing system to adapt to the changing needs of the marketplace (e.g., quickly switching to a more popular product line). In fact, in many industries, the biggest barrier to mass-producing a new product model is the high xe2x80x9cfirst-time-throughxe2x80x9d or xe2x80x9claunchxe2x80x9d cost of modifying work stations to develop new products or components.
With conventional manufacturing systems, unplanned jobs and new products are handled as exceptions, or events that cannot be handled by a workflow. New products typically require a new manufacturing infrastructure, which typically requires approximately several months to become operational. Furthermore, there is a significant learning curve to achieve standard levels of performance for new products. This learning curve results in lost opportunity costs. When exceptions arise, operations are in flux, and require timely adaptation in order to respond to the exceptional event or crisis. However, conventional, rigid manufacturing systems have difficulty responding quickly and effectively to changes or unanticipated events (i.e., exceptions to the normal, expected workflow). One typical response is to form new departments to handle exceptions, which guarantees that exceptions will continue to exist, and that the bureaucracy will continue to grow (the stream of exceptions becomes the rationale for the existence of these new departments). Thus there results a significant capital investment since a product-specific manufacturing infrastructure is required (where that infrastructure includes work stations, devices for transporting work-in-process and finished goods, equipment, machines, etc.).
Also long learning curves are required for operators to manufacture new products which result in unplanned jobs. Learning is limited with conventional manufacturing operations, since operator expertise is linked to specific output types and tools. Therefore, operators typically require new training whenever products and components are added or modified. In addition classical progressive lines causes worker idle time. The classical, balanced progressive line (e.g., a conveyor-driven assembly line) regulates the rate of production and enforces a maximum rate of productivity for every operator which cannot be faster than the slowest operator""s rate of productivity. Therefore, all other operators must wait, in varying amounts of time, depending on their own productivity rate. Operators try to complete a job (e.g., install a part) within a fixed time interval. If they cannot perform the job within the allotted time interval, then it is finished at subsequent work stations. This has the advantage of guaranteeing a certain sustained rate of production. However, the disadvantage is that some workers will inevitably exceed the standard rate of production, and must wait, since no worker can go faster than the regulated production rate. Typically, there is a great deal of slack in standard production rates, which are often set below the productivity capacity of most workers (so that the great majority of, if not all, workers can achieve the standard rate).
Conventional operations also make achieving quality costly and increases cycle time. Steady inspection is required to maintain quality. A given individual (or group) would be responsible for all operations pertaining to a given component. In addition, these complex operations often contain common (therefore redundant) sub-operations, which makes it very difficult to modify operations in a coherent fashion. For example, using a conventional manufacturing system, there are separate work centers for manufacturing the various components of the final product. Unfortunately, such operations contain many redundant sub-operations that are performed at multiple work centers. When a process is modified at one work center, it should also be modified at the other work centers, in order to ensure consistent quality.
Ensuring consistent quality across redundant operations can be accomplished only using quality control techniques that are external to the operations themselves (e.g., statistical process control) and an additional management layer, which adds to the bureaucracy. In addition, redundant operations may compete for common resources (e.g., machines, or even human expertise), thereby introducing unnecessary resource sharing and scheduling problems. These difficult scheduling problems create large work-in-process queues at most activity centers, resulting in increased cycle time. Modular manufacturing exacerbates the fundamental limitations of line manufacturing. Modular manufacturing uses smaller production lines, which creates unrelenting quality concerns due to the greater vulnerability of these lines to absenteeism and sub-standard individual performance.
In recent years, the concept of xe2x80x9clean manufacturingxe2x80x9d has gained popularity. The fundamental essence of lean manufacturing is its xe2x80x9cbackward-chainingxe2x80x9d, or goal-driven (pull) operation, where reasoning starts xe2x80x9cbackwardxe2x80x9d from the goal (in this case, the demand pull). All other lean manufacturing characteristics are derivable from this fundamental lean axiom. Implementations of lean manufacturing employ the principle of xe2x80x9cproduction levelingxe2x80x9d, which generates production plans relative to a xe2x80x9cbatchingxe2x80x9d time interval (this time interval is typically about one month). Since planning production over small time intervals (for example, daily, or even hourly intervals) is considered to be infeasible due to its complexity, production leveling is considered to be necessary in order to make lean manufacturing practical. Unfortunately, the practice of production leveling constrains the ability of the factory to respond quickly to change (i.e., within a very small time interval), on a systematic basis (i.e., without expediting). (A capability for rapid response to change would promise to increase sales by rapidly adjusting production to satisfy demand spikes.) xe2x80x9cFlexibilityxe2x80x9d associated with lean manufacturing is based on various ways of re-shuffling personnel. Cross-training enables personnel to be re-assigned to a variety of production lines (to respond to demand fluctuations). However, there is typically a significant learning curve when operators begin work on a new production line. Overtime increases the capacity of a production line (to respond to increased demand). Layoffs reduce the capacity of a production line (to respond to reduced demand). Lean manufacturing, however, does not overcome the fundamental rigidity of conventional manufacturing, as lean production lines are still xe2x80x9cfixedxe2x80x9d in the sense that they are dedicated to a specific product or model. Switching a line over to a new product still incurs significant xe2x80x9cfirst-time throughxe2x80x9d or xe2x80x9claunchxe2x80x9d costs and delays. Therefore, a factory""s capacity to produce a given product is constrained by the capacity of the production line associated with that product.
In U.S. Pat. No. 5,765,988 there is disclosed a continuous apparel-sewing manufacturing system which is specifically directed to shape-adjustable apparel and discloses the use simultaneous manufacture at a series of work centers located around a single staging area.
In view of the above-identified and other deficiencies found in prior art manufacturing systems and methods, there is a need for a new and improved manufacturing plant, system and method which overcomes these deficiencies which is particularly applicable to rigid-body manufacturing.
In general, it is an object of the present invention to provide an alignment-based rigid-body manufacturing plant, system and method in which manufacturing operations are categorized in generic categories of dynamically occurring alignments of core operations.
Another object of the invention is to provide a plant, system and method of the above character in which these generic categories of alignments transcend a particular type of output from the manufacturing plant and the tooling utilized in the manufacturing plant.
Another object of the invention is to provide a plant, system and method of the above character in which the generic categories of alignments may be utilized to manufacture a wide variety of products and in which each product is manufactured with the use of specific sequences of these generic categories of alignments of core operations.
Another object of the invention is to provide a plant, system and method of the above character in which plants are formed into alignment units.
Another object of the invention is to provide a plant, system and method of the above character in which each alignment unit is comprised of at least three work stations and at least two operators.
Another object of the invention is to provide a plant, system and method of the above character in which each work station is capable of being associated with one or more alignment-based manufacturing operations.
Another object of the invention is to provide a plant, system and method of the above character which utilizes a mobile rotating work force in which the operators are permitted to work at their own speed.
Another object of the invention is to provide a plant, system and method of the above character in which operator rotation is used to eliminate idle time and to avoid conflicts of interest.
Another object of the invention is to provide a plant, system and method of the above character in which an operator at one work station after completing an alignment-based manufacturing step at that work station can advance to another work station to perform another alignment-based manufacturing operation.
Another object of the invention is to provide a minimal if not zero operator idle time thereby resulting in increased productivity while maintaining sustained production rates.
Another object of the invention is to provide a plant, system and method of the above character in which short runs can be readily assimilated.
Another object of the invention is to provide a plant, system and method of the above character in which short runs are made feasible by substantially zero set-up costs being incurred at the work stations while still retaining the ability to switch products and styles, thereby making it possible for a production line to simultaneously produce diverse types of products, i.e. in batches of arbitrary size and even batches of one without incurring significant learning curves for the operators or first-time through or launch costs.
Another object of the invention is to provide a plant, system and method of the above character in which the core operations do not require modification to produce a new style with the result that core operations which may require quick adjustments to operating parameters are essentially unchanged.
Another object of the invention is to provide a plant, system and method of the above character in which flexible manufacturing and production of small lots of arbitrary product mix can be readily accomplished and in which successive items being manufactured may be different models without the maintenance of large inventories of work-in-process.
Another object of the invention is to provide a plant, system and method of the above character in which short cycle times can be readily achieved because of the elimination of long set-up times when switching between products.
Another object of the invention is to provide a plant, system and method of the above character in which unplanned jobs and new products can be handled routinely.
Another object of the invention is to provide a plant, system and method of the above character in which the generic categories of alignment operations are applicable to any type of product that is a rigid body.
Another object of the invention is to provide a plant, system and method of the above character in which quality continuously improves because the operators become expert alignment specialists capable of performing alignments with similar dynamics on a variety of components, subassemblies and final assemblies.
Another object of the invention is to provide a plant, system and method of the above character in which average operators are capable of achieving high levels of quality, reversing the existing trend where highly skilled operators achieve only standardized levels of quality.
Another object of the invention is to provide a plant, system and method of the above character in which the alignment-based manufacturing operations are self-correcting because they contain no redundancies because a unique work center and therefore unique individuals are always responsible and therefore accountable for the result.
Another object of the invention is to provide a plant, system and method of the above character in which quality deviations can be readily detected by the next work center or station in the flow because typically the next operation or sequence cannot be performed if the previous operation was performed poorly or incorrectly, reducing the need for reliance on external quality control monitoring.
Another object of the invention is to provide a plant, system and method of the above character in which sudden increases in demand can be readily accommodated by dynamically adjusting the product mix which is feasible because of the nearly zero set-up cost and time.
Another object of the invention is to provide a plant, system and method of the above character in which a significant reduction in training costs of operators can be readily obtained by focusing training efforts on each of the generic alignment-based operation categories, thereby avoiding cross-training on a wide variety of specific products and styles.
Another object of the invention is to provide a plant, system and method of the above character which makes possible improved ergonomics because operators although performing a series of alignments of the same type, these alignments are performed by a dynamically varying mix of specific styles and subassemblies, thereby eliminating the probability of repeating muscle movement sequences and thereby reducing the risk of repetitive strain injuries.
Another object of the invention is to provide a plant, system and method of the above character which by providing operators with alignment specialties results in less monotony and repetitiveness for the operator.
Another object of the invention is to provide a plant, system and method of the above character in which flexible working hours can be readily accommodated because the manufacturing hours can be arbitrarily spread over the manufacturing plant""s up time since a production line can operate efficiently even without full attendance.
Another object of the invention is to provide a plant, system and method of the above character in which material delivery constraints can be relaxed because since the operators are mobile and can move from station to station, the operators can pick up parts over a wider area during their movements between work stations.
Another object of the invention is to provide a plant, system and method of the above character in which continuous manufacturing is undertaken with alignment units that are self scheduling requiring no external scheduling or expediting.
Another object of the invention is to provide a plant, system and method of the above character in which work-in-process queues are used whereby priorities are fully determined by the order in the queue, resulting in a continuous flow of items from the work-in-process queue to the work stations.